1. Field of the Invention
The present invention relates to a process for the preparation of yeast immobilized in alginate beads, immobilized yeast prepared by such process, and a method of preparing fermented liquids using such immobilized yeast.
2. Discussion of the Background
For the preparation of alcoholic drinks, such as, for example, beer, wine or sparkling wine, fermentation is carried out with the aid of yeast. When the fermentation is complete, the yeast must be removed completely to avoid cloudiness of the drinks.
Sparkling wine is prepared by means of a second fermentation of wine to which sugar and particular yeast strains have been added. The fermentation of sparkling wine takes place either in the commercially available champagne bottles, in larger special bottles or in steel tanks. In the case of fermentation in bottles, removing the yeast when the fermentation is complete is complicated. The bottle is stored in an inclined position and shaken repeatedly over a substantial period until the yeast sediments have deposited in the bottle neck. The bottle neck is cooled, during which process the sparkling wine together with the yeast freezes. The bottle is then opened, and the ice plug containing the yeast sediment is squeezed out of the bottle by the internal pressure.
According to FR 2,432,045, above-described process can be simplified. In FR 2,432,045, yeast cells which are enclosed in a calcium alginate gel and which deposit in the bottle neck without shaking are used.
According to EP-A-0,173,915, yeast cells for the production of sparkling wine are immobilized in alginate beads, after which the beads are coated with a cell-free calcium alginate layer, with the intent to ensure that no yeast cells are freed from the immobilisate.
DE-C-2,835,875 describes a complicated process for the preparation of pressure-resistant biocatalysts. Among others in this process, alginate beads containing yeast cells are solidified, washed with a physiological solution of sodium chloride, dried, shrunk and hardened. However, no mention is made in this publication of the production of sparkling wine.
Thus, if champagne yeasts are immobilized in calcium alginate, either no precautions are taken, or complicated measures are taken to avoid the dullness caused by liberated yeast cells. Accordingly, there remains a need for a simplified process for preparing immobilized yeast, which has good settling properties, and does not result in the escape of the yeast from the immobilisate; and the immobilized yeast prepared by such a process. There is also a need for a method of producing fermented liquids utilizing such immobilized yeast.